いくつ
いくつ · ikutsu · JLPT N5 · adverb
how old
🔢 iku (how much, as in ikura) + tsu (counter, as in hitotsu) = how many
The iku- stem asks about amount, the same one in ikura (how much). The -tsu ending is the native counter from hitotsu, futatsu, mittsu. Since ages can be counted with that same series, oikutsu also asks how old someone is.