gill (n.1)
"organ of breathing in fishes," early 14c., of unknown origin, perhaps from a Scandinavian source, such as Old Norse giolnar which perhaps means "gills;" Old Danish -gæln (in fiske-gæln "fish gill"). Related: Gills.
gill (n.2)
liquid measure (commonly a half-pint), late 13c., from Old French gille, a wine measure, and directly from Medieval Latin gillo "earthenware jar," of uncertain origin.
Gill
fem. proper name, see Jill.