fully concealed self-drawn win
A mahjong yaku: winning on a self-drawn tile while the hand has remained completely closed (no calls made).
from Chinese mén qián qīng zì mō hú
Menzenchin tsumohō is a yaku that is completed when you draw the winning tile with a fully concealed hand.
From Chinese 門前清自摸和 (mén qián qīng zì mō hú), a mahjong term. The exact historical derivation within Japanese mahjong terminology is uncertain.