To engage in repetitive behaviors such as eye-poking, skin-picking, hand-biting, or head-banging.
Origin
From Middle English sib, from Old English sibb ("related, akin, sib"), from Proto-Germanic *sibjaz ("related"), from Proto-Indo-European *sebʰ-, *swebʰ-. Cognate with West Frisian besibbe ("related"), Middle Dutch sibbe ("related"), Middle Low German sibbe ("related"), Middle High German sippe ("related"), Icelandic sifi ("related").
From Middle English sib, sibbe, from Old English sibb ("relationship; gossip; friendliness, kindness; love, friendship, peace, concord, unity, tranquility; peace of mind; a relative, kinsman, kinswoman"), from Proto-West Germanic *sibbju, from Proto-Germanic *sibjō ("kinship"), from Proto-Indo-European *sebʰ-, *swebʰ-.
Cognate with West Frisian sibbe ("relative, family member"), Dutch sibbe ("sib"), German Sippe ("tribe, clan"), Icelandic sifjar ("in-laws"), Latin suus ("one's own").
From Middle English *sibben, *sibbien, from Old English sibbian ("to make peace; rejoice"), from Proto-Germanic *sibjōną ("to reconcile"), Proto-Indo-European *sebʰ-, *swebʰ-. Cognate with German sippen ("to be in relationship with, become related to").