Sol
late 19th century: abbreviation of solution.
wiktionary
From Middle English sol(“fifth degree or note of Guido of Arezzo’s hexachordal scales”), [1] the first syllable of Latin solve(“to remove; to get rid of”), the first word of the fifth line, third verse (“Solve polluti, labii reatum”, that is, “Clean the guilt from our stained lips”) of the famed medieval hymn Ut queant laxis, which solfège was based on because its lines started on each note of the scale successively. [2]
Borrowed from Old French sol(“French coin”) (modern French sou), from Latin solidum, the accusative singular of solidus(“Roman gold coin; (adjective) solid”), [3] ultimately from Proto-Indo-European *solh₂-(“whole”). Doublet of sold, soldo, solidum, and sou.
Borrowed from Spanish sol(“sun”), [4] from Latin sōl(“sun”), ultimately from Proto-Indo-European *sóh₂wl̥(“sun”). Doublet of Sol and sol, directly from the Latin.
Borrowed from Latin sōl(“sun”); [5] see further at etymology 3. Doublet of sol from Spanish.
Sense 1 (“type of colloid”) is derived from -sol (in words like alcosol and hydrosol), an abbreviation of solution. [6]
Sense 2 (“solution to an objection”) is derived directly from solution. [7]
etymonline
Sol (n.)
"the sun personified," mid-15c. (also in Old English), from Latin sol "the sun, sunlight," from PIE *s(e)wol-, variant of root *sawel- "the sun." French soleil (10c.) is from Vulgar Latin *soliculus, diminutive of sol; in Vulgar Latin diminutives had the full meaning of their principal words.
