expression, ichidan verb
to be of no importance; to be trivial; to not amount to much
Used to dismiss something as insignificant or limited in scale. Often appears as たかが知れている or たかが知れた.
彼の実力なんてたかが知れている。
His ability is nothing to speak of.
そんな小さなミス、たかが知れたことだ。
A small mistake like that is of no importance.
Standard kana-mixed spelling; the たかが part is usually written in kana.
Kanji spelling is possible but less common; the kana form is preferred.
たかが is an adverb meaning 'merely' or 'only', while たかが知れる is a verb phrase meaning 'to be trivial'.
From たかが (adverb meaning 'merely') + 知れる (to be known). The literal sense is 'it is known to be merely...', which developed into 'it is of no importance'.