vagary

oikku, päähänpisto An erratic, unpredictable occurrence or action.
1871, w:Charles Kingsley|Charles Kingsley, At Last: A Christmas In The West Indies, ch. 8:

It now turns out that the Pitch Lake, like most other things, owes its appearance on the surface to no convulsion or vagary at all, but to a most slow, orderly, and respectable process of nature, by which buried vegetable matter, which would have become peat, and finally brown coal, in a temperate climate, becomes, under the hot tropic soil, asphalt and oil.

And then came the day when my socialism grew respectable,—still a vagary of youth, it was held, but romantically respectable.