Where does “islom” come from?

islom (Swedish) comes from Swedish is, from Old Swedish is, from Old Norse íss, from Proto-Germanic īsą, from Proto-Indo-European h₁eyH- — ice, frost.

Ancestry of “islom”, step by step

islom traces back through two separate lines of ancestry.

via Swedish is

StepLanguageWordMeaning
1SwedishisIce; frozen water; Ice; a sheet of ice lying on a...
2Old Swedishis
3Old Norseíssice
4Proto-Germanicīsąice
5Proto-Indo-Europeanh₁eyH-ice, frost

via Swedish lom

StepLanguageWordMeaning
1Swedishloma loon, a diver (bird)
2Old Norsehlummr
Every word from Proto-Indo-European h₁eyH-Every word from Proto-Germanic īsąEvery word from Old Norse íss