The phrase "once twice" is spelled the way it sounds. The first vowel sound is represented by the letter 'o' which is pronounced as /ɒ/ in IPA phonetic transcription. The 'n' represents the consonant sound /n/, 'c' represents /s/ and 'e' represents /ɪ/. The second vowel sound is represented by the letter 't' which is pronounced as /t/. Finally, the last vowel sound is represented by the letter 'w' which is pronounced as /w/. So, "once twice" is spelled as /wʌn(t)s/ /twaɪs/ in IPA phonetic transcription.
The phrase "once/twice" is not a singular word, but rather a combination of two separate words.
The word "once" originated from the Old English word "ānes", which means "one time" or "one occasion". It is derived from the numeral "one" and is related to the German word "einmal". Over time, "ānes" evolved into "once" in Middle English.
Similarly, the word "twice" comes from the Old English word "twīwa", meaning "two times" or "two occasions". It is derived from the numeral "two" and shares its roots with the German word "zweimal". In Middle English, "twīwa" transformed into "twice".
When combined, "once" and "twice" create a phrase used to indicate a specific number of times something has occurred.