a suffix originally occurring in adjectives borrowed from Latin (fictitious); on this model, used with stems of other origin (bumptious).
Also, -ious, -ous.
Origin
< Latin-tiōsus, equivalent to -t(us) past participle suffix + -iōsus -ious
-tiouscompound suffix, repr. L. -t-iōsus, consisting of -iōsus, -ious, appended to the -t of a L. participial stem. It thus serves to form adjectives belonging to ns. in -tion, as in ostentation, -tious, ambition, -tious, caution, -tious, contention, -tious, nutrition, -tious, superstition, -tious; but its range is much narrower than that of -tion.
-tious/ʃəs/suffix.
ORIGIN: Repr. Latin-tiosus, combining -iosus-ious with verb stems in -t.
Forming adjectives with the sense ‘full of, characterized by’, corresponding to nouns in -tion, as ambitious, nutritious, superstitious, etc. See -ious, -ous.