The Rendille language is about 80 percent similar to Somali. It's considered as a dialect of Somali and not a separate language. The Jiiddu dialect of Southern Somalia is practically the same as Rendille and speakers of both dialects will have no problem understanding each other. Even for standard Somali speakers, Rendille can be understood with some effort. Look at the following examples in Rendille followed by standard Somali:Interesting. I can barely understand Afar but Rendille is pretty understandable.
inam aa yimi inan baa yimi
us shele yimi isagu shalay buu yimi
us Koor ka yimi isagu Koor buu ka yimi
inam aa yeelaa inan baa yeelayaa
haantii ween haantii weeyneed
an dhafar aa qabaa anigu dhar baan qabaa
Inam aa dheer yehe inankii waa dheer yahay
Inam aa buur yehe inankii waa buuran yahay
Inam ma dheera inanku ma dheera
Inam aa doonaa inan baa doonayaa
dhiri aa kuleel dherigaa waa kulayl
aan urdaa waan hurdaa
aan dawo soo gade anigu dawaan soo gadey or gatey
Aabahaayaa gaal maalaya aabahay baa geel maalaya
us min aa dhisdaa isagu min(guri) buu dhisayaa
walax aan doono meleh waxaan doonayaa maleh
dheri mee dherigii mee
The vocabulary is practically the same but sometimes with a different accent, see the following examples:
abar habar
Ilim ilin
dowoxo dawoco
Ul ul
riy ri'
mantaan mataan
Jid jid
Gaal geel
Min min
War war
Luqum Luqum
As I said these are just examples of the 80 percent vocabulary that Rendille shares with Somali. The other words that we may not understand are probably proto Cushitic words we lost or words borrowed from other people they have interacted with.
They pronounce camel as gaal, while modern Somalis say geel. But theirs is the original pronunciation we lost and which remains in old Somali words or names like Abgaal, the father of camels, Gaal jecel, those who love camels, Hadhuub gaal, camel milk container etc.
Rendille are an offshoot of Somalis and have retained most of the Somali language, despite being surrounded by stronger more powerful non Somali neighbours. Most Somalis remain ignorant of this, but for all practical purposes, If the Rendille were living in , say Southern Somalia, they would be just another Somali clan, speaking a different Somali dialect.