Vagary can be traced to the Latin verb vagārī, meaning “to wander” or “to roam,” and it's likely that vagabond comes from that same source. 

Vagary was first used in English in the late 16th century (also as a verb in the sense ‘roam’).  According to the OED the earliest known use of the noun vagary is in the mid 1500s.  OED's earliest evidence for vagary is from 1566, in the writing of Thomas Blundeville, author and translator. 

Examples of vagary in a sentence: 
"He and his team have delivered despite the vagaries of the weather. 
"It has withstood the test of time and is not prone to the vagaries of passing fads."
"Keyword analysis is a bit more of an exact science, but even that is subject to the vagaries of public opinion and circumstance." 
"The mind has its own vagaries, its ups and downs." 
"Like almost anything else, kitchen décor is seasonal and subject to the vagaries of fashion."

Just the facts:

VAGARY Definition & Meaning - Merriam-Webster