First, the Taboo (as opposed to a taboo) did not exist until Book 7
“Sorry.” said Ron, wrenching Harry back out of the brambles, “but the
name’s been jinxed. Harry, that’s how they track people! Using his
name breaks protective enchantments, it causes some kind of magical
disturbance—it’s how they found us in Tottenham Court Road!”
We see that the name has been jinxed; this is a new development. The opposite would not make any sense: why would the pre-Voldemort Ministry be interested in catching people who said Voldemort's name? Voldemort, on the other hand, knows that only those who stand up to him use his name as a matter of course:
"You’ve got to give them credit, it makes sense. It was only people who
were serious about standing up to him like Dumbledore, who ever dared
use it. Now they’ve put a Taboo on it, anyone who says it is
trackable—quick-and-easy way to find Order members!"
We also see that Hagrid is willing to say the name if necessary
He sat down, stared into the fire for a few seconds, and then said,
"It begins, I suppose, with -- with a person called -- but it's
incredible yeh don't know his name, everyone in our world knows --"
"Well -- I don' like sayin' the name if I can help it. No one does."
"Why not?" "Gulpin' gargoyles, Harry, people are still scared. Blimey,
this is difficult. See, there was this wizard who went... bad. As bad
as you could go. Worse. Worse than worse. His name was..."
Hagrid gulped, but no words came out.
"Could you write it down?" Harry
"Nah -can't spell it. All right -- Voldemort. " Hagrid
shuddered. "Don' make me say it again. Anyway, this -- this wizard,
about twenty years ago now, started lookin' fer followers. Got 'em,
too -- some were afraid, some just wanted a bit o' his power, 'cause
he was gettin' himself power, all right. Dark days, Harry. Didn't know
who ter trust, didn't dare get friendly with strange wizards or
witches... terrible things happened. He was takin' over. 'Course, some
stood up to him -- an' he killed 'em. Horribly. One o' the only safe
places left was Hogwarts. Reckon Dumbledore's the only one
You-Know-Who was afraid of. Didn't dare try takin' the school, not
jus' then, anyway."
I'm sure there were many other wizards, particularly when people still though Voldemort was gone, who were willing to say Voldemort's name, but simply very reluctant to do so. The setup would be very similar. Young children would wonder why, for example, their relatives were dead. (Remember that many wizarding families lost relatives in the first war in Britain). Then their parents would have to tell them, and would reluctantly hand over Voldemort's name.
Don't forget: Voldemort is a constant topic of conversation.
When a massive war happened barely a decade before, the phrase "You-Know-Who" will be on everyone's lips. Once a child has picked up a modicum of language, it would only be natural to say, "No, I don't know who." And then their parents have to explain to them in hushed voices who they are actually talking about, and not to say his name. Most people, I imagine, were not so devoted to not saying Voldemort's name that they would refuse even to whisper it to their children. I suspect that most people could write it down, to start with.
And that's really the answer: Voldemort is someone that you need to know about. People may use euphemisms, but they know his real name. It's a bit like how people often used to say "passed away" instead of died, almost uniformly, for the sake of politeness, but everyone still knew the name of death.