This sound change explains why we have both tea and cha readings for the character 茶.
The character was pronounced as /*lˁra/ in Old Chinese, and another sound change first made that /ta/, meaning both 荼 and 茶 were the same thing. The character 茶 was invented much later. From /ta/ we got Taigi’s tê. The t > ts sound change gave us cha and caa in Mandarin and Cantonese.