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ingenuous [ingenuous 词源字典]: ingenuous: [16] Etymologically, ingenuous means ‘inborn’. English acquired it from Latin ingenuus, which was composed of the prefix inand the element *gen-, denoting ‘production, birth’. This was originally used for ‘born in a particular place, native, not foreign’, but it soon began to take on connotations of ‘freeborn, not a slave’, and hence ‘of noble birth’.

Metaphorical transference to qualities thought characteristic of the nobility – uprightness, candour, straightforwardness, etc – soon followed, and that was the word’s semantic slant when English acquired it. By the 17th century, however, it had started to slide towards ‘artlessness, innocence’ (a sense reflected in ingénue, borrowed from French in the 19th century).
=> gene, general, generate, genital, ingénue[ingenuous etymology, ingenuous origin, 英语词源]
straightforward (adj.): 1550s, "directly forward, right ahead," from straight (adj.1) + forward (adv.). In reference to language, from 1806. Related: Straightforwardly; straightforwardness.