Rhonda

Per Wikipedia: Sir Ifor Williams, in his work Enwau Lleoedd, suggests that the first syllable rhawdd is a form of the Welsh adrawdd or adrodd, as in "recite, relate, recount", similar to the Old Irish rád; 'speech'. The suggestion is that the river is speaking aloud, a comparison to the English expression "a babbling brook".

I thought it meant something to do with "spear". Is that not true anymore?

I'm a bit skeptical of the idea that Rhondda, either in terms of the place name or the particular feminist, was an influence on this name, because since the very beginning the spelling "Rhonda" has been the one used for girls, and "Rhondda" has been practically non-existent. If the name was originally intended to honor a place or person named Rhondda, surely some of the early examples of women with the name would have that spelling. :)

I once read in a very popular baby name book, 10,000 Names For Babies, Rhonda means "powerful river". I like that meaning better.

"10,000 Names for Baby" may be popular, but it's wholly inaccurate when it comes to the meaning of this name. "Powerful river" is a completely false meaning, as far as I can tell from my research. Most books and sites that have the word "baby" in their title can't be trusted. It's sad, but true.