pauldron

From earlier pouldron, poleron, paleron from Middle English polron, palerns, pollerons. This may have been borrowed from Old French paleron, which derives from elements corresponding to French pale (“blade (of a shovel, etc)”) + -eron but was semantically influenced by Old French espaule (“shoulder”) (whence French épaule). Alternatively, some references derive the Middle English word from Middle French espalleron, espauleron, from Old French espaule. Although a form with d at the end is found in Middle English (polrondys, compare Early Modern English polrynges c. 1550), the interpolation of a d between the l and the r dates to the 1500s; the d, and the preference since the early 1800s for the spelling and pronunciation with paul- rather than poul-, may be due to the influence of spaulder.

来源：wiktionary