entries → 難怪
TSUMUGU · TOCFL B1 (est.) · 詞
難怪 word · TOCFL B1 (est.)
難怪 ＝ 難 ＋ 怪
ㄋㄢˊ ㄍㄨㄞˋ · nánguài
adverb — no wonder; that explains it

字源 FORM — what the parts do

難hard / difficult (困難)nán
怪to blame (責怪)guài
難怪，困難的難，責怪的怪。

故事 STORY — a scene to remember it by

知道原因，就難以責怪了。
Once the reason is known, it is hard (難) to blame (怪) — no wonder.
記憶法
關 · Related
原來yuánláithe realization that pairs with it — "so that's why"怪不得guàibùdéa near-synonym — also "no wonder"