Insula

The latin word insula is related to

Gaelic/Irish;ennis/innis,sometimes angalised to Inch eg Enniskillin
Greek;nesi,nesos, believed to be pre-greek
Welsh;ynys

There is a village called Insula in the Ahr valley, rhineland

Ablative/Ablaut grammer in Indo-european languages

Examples are

sang
sing
song
sung

The vowel varies according to meaning.