sparrow fart (sparrowfart, sparrow fart, sparrow’s fart)
humorous expression (UK, Australia, NZ)

- a time very early in the day; dawn

- A person or thing of no consequence.

YourDictionary

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The earliest time of the morning. About the time when all the sparrows get up and let out a little fart signifying their awakening.

Urban Dictionary

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ORIGIN

According to the veteran chronicler of English slang Jonathon Green, the expression “sparrow’s-fart” is a late 19th-century coinage, when country folk knew a thing or two about dawns.

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HISTORICAL SIDENOTES

According to Historic-UK, when the Earl of Oxford made a low bow to the Queen (Elizabeth 1), he happened to let go a loud fart, at which he was so ashamed that he left the country for 7 years. At his return the Queen welcomed him and said, “My lord, I had forgot the fart!”

This story echoes another (excuse the pun) even more hilarious from “A Thousand and One Nights”…

A man let out loud fart in front of the king and was so embarrassed that he left the country for several years. Hoping that everyone had forgotten the incident he returned and asked someone whether the king was still alive. The man replied “No, he died in the year of the Great Fart.”

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SYNONYMS  (very early morning)

aurora, cockcrow, crack of dawn, dawn, daybreak, dayspring, first light, sunrise, sunup

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SMUGGLE OWAD into a conversation, say something like:

“We left home at SPARROW’S FART to go fishing.”
“I’ve been up since SPARROW FART and I’m exhausted.”