Starting from its origin, although only from ancient Egyptian mythology, the first "documented" oral sex was between the Egyptian god-king Osiris, and his sister-turned-wife Isis.

The story goes that when Osiris was murdered and chopped up into pieces by his brother, Set, Osiris’ wife Isis put his body back together, but unfortunately couldn’t find the penis. Clearly thinking: “what’s a man without a penis?” she crafted a makeshift penis out of clay, stuck it onto Osiris’ crotch, and “blew” life into him by sucking his clay penis.
Which is why as they say amazing blowjobs take your breath away even today.

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In Ancient Rome men of status could receive, not give

Now in Old Rome, it was common and acceptable that noble men and soldiers were on the receiving end of the BlowJob, while slaves and lower class women would be giving the job. Even though, the men were seen as the active participant of the act while the woman was seen as passive, as she was the one getting the penis.

Old Greeks guys loved bjs....

In the times of Plato and Socrates, blowjobs were popular and proliferate. BlowJobs were termed playing the flute. Those Greek guys would happily lifted their togas for someone to come along and play their flute and it was common for oral sex to occur between two straight men.

A whole chapter of the Kama Sutra is dedicated to oral sex

In ancient India sucking a mango, not a banana, represented the BJ
In the Kama Sutra, there is a chapter called Auparishtaka, AKA Oral Congress, which gives a step by step guide for sucking dick lol.

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Here’s an interesting passage:

When, in the same way, he puts the half of it into his mouth, and forcibly kisses and sucks it, this is called “sucking a mango fruit"......

This chapter goes into detail on eight different methods to give head, and some of them are very complicated, and they seem like they require some flexibility to practice.

Blowjobs were given as a form of punishment in ancient Rome

In Roman times punishment for breaking the law could be to give the person you wronged a blowjob. In the ruins of Pompeii, archaeologists discovered graffiti that reads Lahis fellat assibus duobus, which translates as Lahis gives head for half a sestence

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Truth About BlowJobs