Ilk. *-os suf. “abstract ending”
Apparently an abstract noun suffix appearing in the words Aros and thalos, perhaps of the same origin as the abstract endings ᴹQ. -sse² and N. -as, though Helge Fauskanger suggested instead that it is related to the locative suffix ᴹQ. -sse¹ (AL-Ilkorin/thalos).
References ✧ Ety/STAL, YAR