Happenstance is a chance occurrence with no plan behind it. Mere happenstance, by happenstance, a happy happenstance.
It is used to deny design — saying something was happenstance rejects the suggestion that anybody arranged it. The word is an American blend of happen and circumstance, first recorded in 1855, and it is one of the tidier coinages of that kind.
1nounhappenstanceA chance occurrence with no plan behind it.
“It was pure happenstance that we sat next to each other on the train and became friends.”
happenstance is a chance event.
A blend of happen and circumstance, attested in American publications from 1855.
Blend of happening and circumstance. Attested from 1855 in US publications.
Etymology from Wiktionary, CC BY-SA