Where does “sofheicseanach” come from?

sofheicseanach (Irish) comes from Irish feicseanach, from Irish -ach, from Middle Irish -ach, from Old Irish -ach, from Proto-Celtic -ākos, from Proto-Indo-European -eh₂ḱos, from Proto-Indo-European -kos — Creates deadjectival and desubstantival...

Ancestry of “sofheicseanach”, step by step

sofheicseanach traces back through two separate lines of ancestry.

via Irish feicseanach

StepLanguageWordMeaning
1Irishfeicseanachvisible
2Irish-achForms nouns from other nouns and adjectives with...
3Middle Irish-achForms adjectives meaning "related to, having,...
4Old Irish-achForms adjectives meaning "related to, having,...
5Proto-Celtic-ākosForms adjectives from nouns and adjectives with...
6Proto-Indo-European-eh₂ḱos
7Proto-Indo-European-kosCreates deadjectival and desubstantival...

via Irish sofheicthe

StepLanguageWordMeaning
1Irishsofheicthevisible
2Irishso-very; X-able, easy to X
3Old Irishso-good
4Proto-Celticsu-good, well
5Proto-Indo-Europeanh₁su-good
6Proto-Indo-Europeanh₁wes-good; to be cheerful, happy; to eat, to feast
Every word from Proto-Indo-European -kosEvery word from Irish -achEvery word from Old Irish -ach