early 15c., omitten, "fail to use or do, fail or neglect to mention or speak of, to disregard," from Latin omittere "let go, let fall," figuratively "lay aside, disregard," from assimilated form of ob (here perhaps intensive) + mittere "let go, send" (see mission). Related: Omitted; omitting.
"neglect or refusal to obey," c. 1400, from Old French desobedience, from Vulgar Latin *disobedientia (replacing Latin inobedientia) from Latin dis- (see dis-) + oboedientia "obedience," abstract noun from oboedientem (nominative oboediens), present participle of oboedire "to obey" (see obey). The English word replaced earlier desobeissance in this sense, and inobedience (c. 1200).
late 14c., disobeien, "neglect or refuse to obey," from Old French desobeir (13c.) "disobey; refuse service or homage," from Vulgar Latin *disoboedire, reformed with dis- (see dis-) from Late Latin inobedire, a back-formation from inobediens "not obeying," from Latin in- "not" + present participle of obedire (see obey). Related: Disobeyed; disobeying.
c. 1600, "to free from obligation;" 1630s, "to refuse or neglect to oblige," from French désobliger (c. 1300), from des- (see dis-) + obliger, from Latin obligare "to bind, bind up, bandage," figuratively "put under obligation," from ob "to" (see ob-) + ligare "to bind," from PIE root *leig- "to tie, bind."
Colloquial sense of "put to inconvenience" is from 1650s (implied in disobligingness). Related: Disobliged; disobliging; disobligingly.
"The fiery cross which in old times formed the rallying symbol in the Highlands of Scotland in any sudden emergency," Gaelic cranntara, cranntaraidh, also (by influence of crois "cross") croistara, croistaraidh, literally "the beam or cross of reproach," from crann "a beam, a shaft" (see crane (n.)) + tair "reproach, disgrace." "[S]o called because neglect of the symbol implied infamy" [Century Dictionary].