Perhaps from eu and tithemi; straight, i.e. (literally) level, or (figuratively) true; adverbially (of time) at once -- anon, by and by, forthwith, immediately, straightway.

see GREEK eu

see GREEK tithemi

εὐθεῖα (eutheia) − 1 Occurrence

εὐθείαν (eutheian) − 3 Occurrences

εὐθείας (eutheias) − 4 Occurrences

εὐθὺς (euthus) − 51 Occurrences