Scholars have long debated the meaning of the name Phol and the word balderes in this verse. Phol is sometimes interpreted as the male half of an otherwise unattested couple : Phol and Volla.
Likewise scholars have argued that the word balderes should be understood as a simple appellation meaning “ lord , ” also otherwise unattested in German . Today , this is a minority view . Rudolf Simek clearly states that “ this is difficult to prove , and therefore the Second Merseburg Charm should continue to be regarded as the first recording of the name Baldr . " John Lindow agrees , stating that “ Frija , the Old High German equivalent of Frigg , participates in the curing of Baldere's ( Baldur's ) horse.956 Not surprisingly then , in the Second Merseburg Charm , we find Odin and Frigg associated with Baldur , their famous son , whose death is a central storyline in later Scandinavian sources .
The verse speaks of an otherwise unknown episode in Old Norse mythology , the laming of Baldur's horse . Baldur's role as a rider is emphasized in the Second Merseberg Charm , in Saxo’s Danish History , and in the eddic poem Lokasenna ….

In the Second Merseburg Charm , balderes horse is injured when Odin and Phol ride into the wood . According to Book 3 of Saxo’s Gesta Danorum , Baldur himself , before his death , was lamed and conveyed about in a carriage. In the same narrative , he is said to open a freshwater well for his men . This ability is closely associated with Baldur's demise : 
“ The conquering Baldur , in order to slake his soldiers , who were parched with thirst , with the blessing of a timely draught , pierced the earth deep and disclosed a fresh spring . The thirsty ranks made with gaping lips for the water that gushed forth everywhere . The traces of these springs , eternised by the name , are thought not quite to have dried up yet , though they have ceased to well so freely as of old . Baldur was continually harassed by night phantoms feigning the likeness of Nanna , and fell into such ill health that he could not so much as walk , and began the habit of going his journeys in a two horse car or a four - wheeled carriage . ” 

This passage may aid our understanding of the name Phol . Saxo informs us that Baldur had the power to open springs , which were called by his name . In Denmark there is Baldersbrønde , “ Baldur's spring , ” in Sjælland , recorded as Baldorpsbrynna in 1321. Benjamin Thorpe states that “ on the right hand side of the road leading from Copenhagen to Roeskilde there is a spring called Baldur's Brönd . ... The tradition among the country people is that it was produced by a stroke of the hoof of Baldur's horse . "
In Germany , we frequently find references to “ Phoľs ” — or “ Fals spring . ” In the province of Thuringia , a Pholesbrunnen is reported . Not far from the Saale river lies a village named Phulsborn . In the Franconian Steigerwald , we find a Falsbrunn . Similarly , we find a Baldersbrunno in the Eifel mountains and in the Rhineland Palatinate , the very regions we discover widespread legends of Frau Holle , Frau Percht , and Frau Goden , who is the wife of Godan or Wodan ( Odin ) . Of the original name of the German village Pfalsau , recorded between 774 and 778 as Pholesauwa or Pholesouwa , Jacob Grimm writes : " Its composition with aue ( auwa ) quite fits in with the supposition of an old heathen worship .
The gods were worshiped not only on mountains , but on “ eas ' enclosed by brooks and rivers , where fertile meadows yielded pasture , and forests shade . Such was the “castum nemus” ( sacred grove ) of Nerthus in an insula Oceani . ” Evidence of such enclosed sanctuaries is found in several Old Norse sources as Oổinsey , Thorsey , Hlessey , etc. Pholesouwa is an Old High German equivalent of names of this type , which means Phols sanctuary.
Thus Phol or Fal is best interpreted as the name of a god . In early Christian times , partial to euhemerism , Baldur was sometimes transformed into a king in Vestphal . According to the Prologue to Gylfaginning , “ Odin's second son was called Beldegg , whom we call Baldr ; he had the country that is now called Westphalia . ” According to ancient belief , nearly all countries and peoples took their names from some ancient ruler : The Franks from Francio , the Angles from Angul , Denmark from Dan , etc. The names Phalen , and Vestphal or Westphalia can be logically explained in the same manner if Baldur was also known as Phol or Fal , and his name was said to have given rise to these districts.
As far as Jacob Grimm could determine , the name Phol was used chiefly by the Thuringians and the Bavarians , although they knew the god by the names Palter or Baldur . The same initial sound shift occurs in the names Perchta and Berchta for Frau Holle . Among the Saxons and Westphalians the names Baldag and Bældæg prevailed. If Phol can be identified with Baldur in the Second Merseburg Charm as the foregoing evidence suggests , then we have a natural explanation of its contents . The events may be seen as a presage of Baldur's death :
One day , Phol ( Baldur ) and his father are out riding with members of their family . The foot of Baldur's horse is sprained , and each family member comes to his aid in order of proximity . Closest is a female rider named Sinhtgunt , probably representing Baldur's wife Nanna , and her sister Sunna ( see further ) . Next comes Frigg , his mother , and her sister , Volla , known as Fulla in the later Icelandic sources . Last comes Odin , Baldur's father , whose superior magic cures the sprain no doubt caused by witchcraft . Thus Baldur appears by two names , Phol and Baldere , in a single verse— a not uncommon phenomenon in old Germanic poetry where , for example , Odin's wife is called Hlin and Frigg in the space of a single strophe , Völuspá 53 [ See Chapter IX : Jörd , Thor's Mother ].

By William P Reaves
Norroena.org
https://norroena.org/product/odins-wife-mother-earth-in-germanic-mythology/