what's the reason all negative verbs in Japanese ends with ない?
is It related to あるverb? I am interested in knowing the origin
ない is the negation suffix.
As a suffix, ない superseded older ぬ.
ない is not related (derivationally) to the verb ある.
As to "why" all plain (non-ます) negative verb forms include ない, may as well ask why all negative verb constructions in English include some form of the word "not".
Separately, regarding the etymology.
The negation suffix ない appears from around the late 1500s, originating in eastern Japanese dialects.
Before that, the negation suffix was ず or inflected form ぬ. Some linguists think that the predicate form ず was itself a contraction of older に [from ぬ] + す [of uncertain function]: //nisu// → //nsu// → //nzu// → //zu//.
In ancient eastern Japanese dialects, there was also a negation suffix なふ. Some scholars suggest a link between ancient なふ and modern ない, but there are problems with this theory -- なふ conjugated as a verb, while ない conjugates as an adjective; also, なふ disappears from the historical record centuries before we see ない.
After ない appeared and began spreading, both ない and ず or ぬ were in use. ない didn't really become standard until after 1907 when official government textbooks settled on using ない.
For those interested, references (in Japanese):