From Proto-Germanic *īsą — and 'icicle' is a hidden tautology, since both halves of the compound originally meant ice.
Frozen water; a solid formed by the freezing of a liquid.
From Old English 'īs' (ice), from Proto-Germanic *īsą (ice), from PIE *h₁eyH-s- (ice, frost). The word has cognates across Germanic but is notably absent from most other Indo-European branches, suggesting that the PIE root may have been rare or that other branches replaced it. The modern pronunciation with a diphthong reflects the Great Vowel Shift, which turned
'Icicle' is a hidden tautology. It comes from Old English 'īsgicel,' where 'īs' means 'ice' and 'gicel' means 'icicle' or 'ice piece.' So 'icicle' literally means 'ice-icicle' — the original word for the hanging ice was 'gicel,' and people added 'ice' in front for emphasis, then forgot that 'gicel' already meant the same thing.