Cf. Amh. tərbe ‘baby elephant’ (AED 966), possibly related to the present root with *-al > *-ay > *-e. If this comparison is accepted, the variant proto-form *tVrbal- should be treated as the primary one. This conclusion seems to be corroborated by Bed. tírbil ‘calf just weaned’ (Blažek 2003 274) which is, admittedly, somewhat remote semantically.