pre-noun adjectival
Colloquial, affectionate pre-noun adjective meaning 'tiny' or 'little'. Often used in casual speech, especially with children or small things. Related to 小っちゃい (chicchai).
See also: 小っちゃい
ちっちゃな犬が庭で遊んでいる。
A tiny dog is playing in the garden.
ちっちゃな頃からピアノを習っている。
I've been learning piano since I was little.
小さい is the standard i-adjective for 'small'. ちっちゃな is more informal and carries a cuter, more affectionate nuance.
Colloquial contraction of 小さい (chiisai), with the pre-noun adjectival form ちっちゃな derived from the i-adjective ちっちゃい. The exact historical development is uncertain, but it likely arose from baby talk or affectionate speech.