From Wiktionary, the free dictionary
Perhaps ხელი (xeli, “hand”) + -ა (-a).
-ხელა • (-xela)
- Attaches to a pronoun in the genitive case to form an adjective denoting equivalence of size; this deletes the pronoun's final -ი or -ის
- მე (me, “me”) + -ხელა (-xela) → ჩემხელა (čemxela, “my size, the same size as me”)
- ეს (es, “this”) + -ხელა (-xela) → ამხელა (amxela, “this large, as big as this”)