google
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late 16th century: from the verb tip2 + -sy.
wiktionary
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From tips + -y. Compare artsy, folksy, and sudsy.
etymonline
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tipsy (adj.)
1570s, from tip (v.1); compare drowsy, flimsy, tricksy. Later associated with tipple. Tipsy-cake (1806) was stale cake saturated with wine or liquor.
