"spring of water," 1590s, probably a shortening of fountain influenced by French font "fount." Figurative use also is from 1590s.

fount on Mount Helicon sacred to the Muses, its waters were held to bestow poetic inspiration, from Greek Hippokrene, earlier hippou krene, literally "horse's fountain," from genitive of hippos "horse" (from PIE root *ekwo- "horse") + krēnē "fountain," which is of uncertain origin.

"complete set of characters of a particular face and size of printing type," 1680s (also fount); earlier "a casting" (1570s); from French fonte "a casting," noun use of fem. past participle of fondre "to melt," from Latin fundere (past participle fusus) "to melt, cast, pour out" (from nasalized form of PIE root *gheu- "to pour"). So called because all the letters in a given set were cast at the same time.