noun
ordinary person; average person; nobody special
Almost always used in negative expressions like 只者ではない or 只者じゃない to mean 'not an ordinary person', implying someone is remarkable, extraordinary, or suspicious.
彼の腕前は只者ではない。
His skill is not that of an ordinary person.
あの男、只者じゃないと思った。
I thought that man was no ordinary person.
Rarely used kanji form.
凡人 is a more formal, neutral term for an ordinary or mediocre person, while 只者 is almost exclusively used in negative constructions to emphasize extraordinariness.
普通の人 is a straightforward, everyday phrase for 'ordinary person', whereas 只者 carries a stronger nuance of being remarkable when negated.
Compound of 只 (tada, 'ordinary, mere') and 者 (mono, 'person'). The reading ただもの is a straightforward combination of the two elements.