Where does “Gamle Oslo” come from?

Gamle Oslo (Norwegian Nynorsk) comes from Norwegian Nynorsk Oslo, from Old Norse Ósló, from Proto-Germanic ansuz, from Old High German helm, from Proto-West Germanic helm, from Proto-Germanic helmaz, from Proto-Germanic halmaz, from Proto-Indo-European ḱolh₂mos — to pierce, strike; to stick; prick; stab.

Ancestry of “Gamle Oslo”, step by step

Gamle Oslo traces back through two separate lines of ancestry.

via Norwegian Nynorsk Oslo

StepLanguageWordMeaning
1Norwegian NynorskOslo
2Old NorseÓsló
3Proto-Germanicansuzdeity, god; name of the A-rune
4Old High Germanhelmhelmet
5Proto-West Germanichelmhelmet
6Proto-Germanichelmazhelmet
7Proto-Germanichalmazhalm; stem; stalk; straw; hay
8Proto-Indo-Europeanḱolh₂mosstalk
9Proto-Indo-Europeanḱelh₂-to pierce, strike; to stick; prick; stab

via Norwegian Nynorsk gamal

StepLanguageWordMeaning
1Norwegian Nynorskgamalold
2Old Norseellricomparative degree of gamall
3Proto-Germanicalþizôcomparative degree of *aldaz
4Proto-Germanicaldazold, grown up
5Proto-Indo-Europeanh₂eltós
6Proto-Indo-Europeanh₂él-to grow, nourish
Every word from Proto-Indo-European ḱelh₂-Every word from Proto-Indo-European ḱolh₂mosEvery word from Proto-Germanic halmaz