"oft-times" means: An archaic or literary adverb meaning 'often' or 'many times' — now only encountered in deliberately formal, poetic, or old-fashioned writin.... This is technical or formal vocabulary, more likely to appear in school work, news or a particular profession than in peer chat. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your child uses the term, it is usually a sign of curiosity about a subject area. A short follow-up question about where they came across it is usually all that is needed.