What is the X in X-mas?
mid-14c., talwgh, from a form cognate with Middle Low German talg "tallow," Middle Dutch talch, from Proto-Germanic *talga-, meaning perhaps originally "firm, compact material" (cf. Gothic tulgus "firm, solid").
odourless, tasteless, waxy white fat, consisting of suet (the hard fat about the kidneys and loins of cattle, sheep, and horses) or similar vegetable substances. Tallow consists mainly of glyceryl esters of oleic, palmitic, and stearic acids. Tallow was used chiefly to make soap and candles until the development of synthetic surfactants made it available for animal feeds and as a base for chemicals and lubricants. Tallow is extracted by rendering, cutting, or chopping the fatty tissue into small pieces that are boiled in vats or cooked in steam digesters, then collecting the fat by skimming or by centrifuging.