Notes: Reconstructed for the PEC level. The same stem possibly can be discovered in Lak. cu-ma 'who, which' (a compound with cu 'who'). Note a striking parallelism between PL *mo-sa 'when' and PN *ma-ca(n) id.
[Since initial *mu- must be regularly dropped in Lak., it would be possible to derive Lak. ta 'when' < *mu(r)-ta = PD *mu-rt].