(…) When Roman writers spoke of the gods and goddesses of other peoples, they generally tried to identify them with deities from their own religion. When they mentioned Odin, they glossed him as Mercury, the Roman psychopomp (the divine figure who guides those who have just died from the realm of the living to that of the dead, and, in due time, back to the land of the living again).[18] This is significant, because it shows that Odin’s associations with death were seen as being even more significant than his associations with war, or else he would have been glossed as Mars. (This designation usually fell to Tyr or Thor instead.)
Interpretatio germanica is the practice by the Germanic peoples of identifying Roman gods with the names of Germanic deities. According to Rudolf Simek, this occurred around the 1st century of the Christian era, when both cultures came into closer contact. Some evidence for interpretatio germanica exists in the Germanic translations of the Roman names for the days of the week (…)
In most of the Romance languages, which derive from Latin, days of the week still preserve the names of the original Roman deities, such as the Italian for Tuesday, "martedì" (from the Latin "Martis dies"). This is also the case with Saturn in some West Germanic languages; such as the English "Saturday," the West Frisian "Saterdei", the Low German "Saterdag" and the Dutch "zaterdag" all meaning Saturn's day[1].
Simek emphasizes the paucity of evidence and notes that comparison with Roman gods is insufficient to reconstruct ancient Germanic gods and equate them definitively with those of later Norse mythology.[11]