"pendent mass of ice tapering downward to a point, formed by the freezing of drops of water flowing down from the place of attachment," early 14c., isykle, from is "ice" (see ice (n.)) + Middle English ikel, a word that by itself meant "icicle," from Old English gicel "icicle, ice" (found in compounds, such as cylegicel "chill ice"), from Proto-Germanic *jekilaz (source also of Old Norse jaki "piece of ice," diminutive jökull "icicle, ice; glacier;" Old High German ihilla "icicle"), from PIE *yeg- "ice" (source also of Middle Irish aig "ice," Welsh ia). Dialectal ickle "icicle" survived into 20c.
The latter element came to lose its independent meaning, and has suffered under popular etymology; explained in books as a mere dim. termination -icle, as in article, particle, etc., it appears transformed in the obs. or dial. forms ice-sickle, ise-sicklc, ice-shackle, ice-shoggle, OSc. iceshogle, icechokill, etc. [Century Dictionary]