偶々
たまたま · tamatama · JLPT N3 · adverb
by chance
🎲 たま (rare, as in たまに) doubled: rare-rare = it just happened by chance
偶 is the 'chance' kanji from 偶然 (gūzen, coincidence), and 々 repeats it. たまに means 'once in a while'; doubling it to たまたま means it happened only this one time, by luck.