Sip
late Middle English: perhaps a modification of sup1, as symbolic of a less vigorous action.
wiktionary
From Middle English sippen, of uncertain origin. Compare with Low German sippen(“to sip”). Possibly from a variant of Middle English suppen(“to drink, sip”) (see sup) or perhaps from Old English sipian, sypian(“to take in moisture, soak, macerate”), from Proto-Germanic *sipōną(“to drip, trickle”), from Proto-Indo-European *seyb-(“to pour out, trickle, leak out”). Compare also Old High German supfen(“to drink, sip”), from Proto-Germanic *sūpaną(“to sip, intake”).
etymonline
sip (v.)
late 14c., of uncertain origin, perhaps from a source related to Low German sippen "to sip," or from Old English sypian "absorb, drink in," related to supan "to take into the mouth a little at a time" (see sup (v.2)). Related: Sipped; sipping.
sip (n.)
c. 1500, from sip (v.).
