Morphology: pen+twyn+mawr
Phonetic: pen-two-in-mah-oor
The name appropriately means "top of the large hill"; the village is located above Newbridge on top of a steep hill. It could also refer to the fact that as a larger village than nearby Pen-twyn (near Trinant); the word "mawr" can also mean "greater" or "major" as in Llantwit Major / Llanilltud Fawr in the Vale of Glamorgan.