gentle and reticent
Describes a person who is warm-hearted, calm, and speaks little. Often used to characterize a quiet, dependable personality.
He has a gentle and reticent personality and is trusted by everyone.
My grandfather was gentle and reticent, always with a calm smile.
温厚 means 'gentle' or 'warm-hearted' on its own, without the 'reticent' nuance of 温厚寡黙.
寡黙 means 'taciturn' or 'reticent' on its own, without the 'gentle' nuance of 温厚寡黙.
A compound of 温厚 (gentle, warm-hearted) and 寡黙 (reticent, taciturn). The exact historical derivation is uncertain, but the combination is a natural four-character idiom describing a quiet, gentle personality.