Dr D'Arcy said 'like' developed much like other discourse markers such as 'you know', 'I mean' and 'indeed', which help listeners navigate unplanned, spoken conversation.
She provided three examples of 'like' being used as a conversational marker from around the world more than 100 years ago.
1. And he writes to me. Like until his death, he used to write to me quite frequently. (New Zealand speaker, born 1874)
"Here the like is signalling that the speaker is going to clarify her meaning."
2. They never went out in a small canoe. Like we went from here to Cape Beale. They had great large war canoes. (Canadian speaker, born 1875)
"Here the like is signalling that the speaker is going to elaborate on her point and clarify the first statement."
3. I'd probably missed something you see to begin with. Like I missed one term when I was in the third year at Modern School. (Australian speaker, born 1897)
"Here the like is signalling that the speaker is going to elaborate on the first statement."
So next time you look to judge someone on their use of 'like' in conversation, you might want to, like, not.