Hate to say but it is from a much older culture/language
Good old latin.
Tiro meaning Beginner as in Novice.
[late Middle English: from Latin tiro, medieval Latin tyro ‘recruit’.]
Hence the spelling.
Vague scrape up from old memories of Latin at school
Looked up the spelling point but lots of mangled Latin in English language + a dozen other languages of places England 'ruled/invaded' etc [Long live the Empire .... Cue Music
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