Gallon
Middle English: from Anglo-Norman French galon, from the base of medieval Latin galleta, galletum ‘pail, liquid measure’, perhaps of Celtic origin.
wiktionary
From Middle English gallon, galoun, galun, from Old Northern French galun, galon(“liquid measure”) (compare Old French jalon), from Late Latin galum, galus(“measure of wine”), from Vulgar Latin *galla(“vessel”), possibly from Gaulish[Term?], ultimately from Proto-Indo-European *kel-(“goblet”). Cognate with Ancient Greek κύλιξ(kúlix, “cup”), Sanskrit कलश(kalaśa, “jar, pitcher; measure of liquid”). Related to Old French gille(“wine measure”) (from Medieval Latin gillō(“earthenware jar”)), Old French jale(“bowl”), Old French jaloie(“measure of capacity”).
etymonline
gallon (n.)
English measure of capacity (containing four quarts), usually for liquids, late 13c., from Old North French galon, corresponding to Old French jalon, name of a liquid measure roughly equivalent to a modern gallon," which is related to (perhaps augmentative of) jale "bowl," from Medieval Latin or Vulgar Latin diminutive form galleta "bucket, pail," also "a measure of wine," a word of unknown origin, perhaps from Gaulish galla "vessel."
