availing (adj.)youdaoicibaDictYouDict[availing 词源字典]
"advantageous," early 15c., present participle adjective from avail (v.).[availing etymology, availing origin, 英语词源]
failing (n.)youdaoicibaDictYouDict
late 14c., "failure;" 1580s, "defect, fault," verbal noun from fail (v.).
prevailing (adj.)youdaoicibaDictYouDict
1590s, "vigorous;" 1680s, "widely accepted," present participle adjective from prevail (v.).
railing (n.)youdaoicibaDictYouDict
"construction in which rails form an important part," early 15c., verbal noun from rail (v.2). Technically, railings (late 15c.) are horizontal, palings are vertical.
retailing (n.)youdaoicibaDictYouDict
mid-14c., verbal noun from retail (v.).
sailing (n.)youdaoicibaDictYouDict
Old English seglinge, verbal noun from the source of sail (v.).
unavailing (adj.)youdaoicibaDictYouDict
"ineffectual, useless," 1660s, from un- (1) "not" + availing. Also see unavailable.
unfailing (adj.)youdaoicibaDictYouDict
late 14c., "never coming to an end, unceasing, everlasting, inexhaustible," from un- (1) "not" + present participle of fail (v.). Related: Unfailingly.