monstrous (adj.)youdaoicibaDictYouDict[monstrous 词源字典]
mid-15c., "unnatural, deviating from the natural order, hideous," from Middle French monstrueux, from Latin monstruosus "strange, unnatural, monstrous," from monstrum (see monster). Meaning "enormous" is from c. 1500; that of "outrageously wrong" is from 1570s. Earlier form monstruous (late 14c., from Old French monstruous) was "very common in the 16th c." [OED].[monstrous etymology, monstrous origin, 英语词源]