It’s called a walkie talkie because you can walk while you talk, the name is that literal.
The walkie talkie meaning is hiding in plain sight: it’s a radio you can carry while walking, and you talk into it. Walkie. Talkie. That’s the whole etymology. The name stuck in the 1940s when soldiers first carried handheld radios in the field.
So why is it called a walkie talkie and not something fancier? Because the engineers who built the first ones were playful. Before that, radios were big, heavy, and bolted to vehicles. A portable one that fit in your hand was genuinely new, and it needed a name a soldier could shout across a camp.
Real quick, on the spelling question: how do you spell walkie talkie? Two words, no hyphen, is the standard. You’ll also see walkie-talkie with a hyphen, and both show up in dictionaries. Nobody is going to fail you for either version, honestly.
The name is kind of goofy. But so are the things themselves, in the best way. If you want to see what eighty years of that tradition produced, browse the radio lineup section. And if you have more questions like this one, our FAQ is the place.