Proto-Indo-European *akʷ-ā- "water" became Latin aqua. Combined with ex- "out", it became *exaquāria, becoming Old French sewiere "channel to carry off overflow from a fishpond".
*akʷ-ā- became Proto-Germanic *aǥwiō (AHD) or *ahwiō- (OED) then *aujō- "thing on the water". This became Old English īeġ "island". This combined with land to form īeġland - the s was added to the word sometime after the 15th century because it was thought to be related to isle.
*akʷ-ā- is also found in the name of the glacier covering the troublesome Icelandic volcano, Eyjafjallajökull. Ey is "island", from Proto-Germanic *aujō-. Fjöll is "mountain", from PIE *peli-s- and cognate with English fell "mountain". Jökull means "glacier" and is from PIE *i̯eg- "ice", and I think is exactly cognate with Old English ġicel "ice", which became the -icle in icicle.