Starting in the early second century BC , Roman writers began to represent the voiceless aspirated obstruents of Greek words used in, or borrowed into, Latin, by means of the addition of to the relevant sign for the obstruent, thus: , , . Almost from the beginning, however, they also used this combination of graphemes in non-Greek words, as demonstrated by triumphans (CIL 12.626, about 145 BC) . Scholars have observed that this usage does have a phonetic element, being most common adjacent to a sonorant, but does not give the impression of being a regular sound change. It is best explained, I maintain, as the result of hypercorrection.