pillar: [13] Pillar comes ultimately from Latin pīla ‘pillar’ (source also of English compile, pilaster [16], and pile ‘heap’). In Vulgar Latin this was extended to *pīlāre, which passed into Anglo-Norman piler. This was the form in which English originally acquired it, and the -ar ending was not grafted on to it until the 14th century. => compile, pilaster, pile
