holm (n.)

"small island in a river; river meadow," late Old English, from Old Norse holmr "small island," especially in a river or bay, or cognate Old Danish hulm, from Proto-Germanic *hul-maz, from PIE root *kel- (2) "to be prominent; hill." Obsolete, but preserved in place names, where it has various senses derived from the basic one of "island:" "'raised ground in marsh, enclosure of marginal land, land in a river-bend, river meadow, promontory'" ["Cambridge Dictionary of English Place-Names"]. Cognate Old English holm (only attested in poetic language) meant "sea, ocean, wave."