The interjection 'ta' is an informal British expression of gratitude. It is believed to have originated as a child's word, a simplified form of 'thank you'. Its first recorded use dates to the late 18th century. The word's journey exemplifies a common linguistic process where a longer, more formal phrase is clipped and adopted into casual, colloquial speech, eventually becoming a standard informal term.

This word is a simplex interjection and cannot be meaningfully segmented into constituent morphemes based on its modern English spelling.