lit. 300 silver taels not hidden here (idiom); fig. to reveal what one intends to hide
Definitions (粵典–words.hk)
語句
古時有個故事，講一個人掘咗個窿埋咗啲錢喺入面，佢收好啲錢之後，仲係驚有人會揾到，於是插咗個牌係度，上面寫住「此地無銀三百兩」。唔使審，之後啲錢梗係畀人偷晒啦。後來用嚟比喻人明明想掩飾一啲嘢，但係愈掩飾愈露出馬腳。有時縮寫做「此地無銀」。 to expose something by hiding it; to try to hide something but instead reveal it; in short 此地無銀
參看
此地無銀三百両
Definitions (Wiktionary)
phrase, idiomatic
a clumsy denial resulting in self-exposure; a very poor lie which reveals the truth; protest one's innocence too much; the lady doth protest too much