They come when languages sleep with each other. In quantum mechanics its called mixing. [there is a detailed mathematical chart I have given of consonant and vowel definition, when they change their place for any reason whatsoever it would be called mixing in mathematical language and sex-of-language in ordinary language ]
The origin of the word agni, ignus, ignite etc [Fire] The agni is said to be the original sanscrit. [In sanscrit nothing is an orginal if you apply quantum-mechanics aka mixing of language, because soon you will lose track of which came first g or y? which can be accented in various ways, being a base in various different languages over millenia and alternating to each other million times] How is it mixing here? take the case of g in Agni [accented: g in egg] But you realize that g is possible as in Germany [J] and j can alternate to y/i as in champagne. [even to d as soldier d is a j therefore g.] so it is actually ain/ayin etc. now consider the fact closely placed letters will just flip [try speaking any word and be a bit flexible with phonetics you will see phonetic elements: letters/consones/vowels etc swap places among each other] So ayin >> ani, anji, angi, anyi etc [n could b nasal-n also ] This is what it is for other archaic/ancient words for fire, eg Odia: nian [nina, if both n are nasal ina/ian] anch [anj, anjo] also Japanese, fire: enjou. Hindi: ag [but actally ai, ayi with addition to nasal-n becomes ayin, anjo etc ] So all these words for fire are the same word. Only recently the g is said like its in egg [more likely because only in Hindi its said like that, because of lack of understanding of the actual Roman-transLIT. Actually this is because Hindi often sleeps with English and wants to force these fanatically over all other Indian language-forms which are quite far ancient than Hindi. Other languages are not lesser culprits, they do not do their home work before accepting something. When they do Hindi has to bend. Actually Hindi also sleeps with many other languages. She says its a learning experience.] This is the reason why ignus, ignite with g as in egg. Its a self-denial to Roman.
Now think this phrase: anjani putra paban sut nam.
This means “one whose mother is anjani and father is wind” son of anjni and wind. Hanuman. But actually anjani, ajani, agni, enjou or Fire. Hanuman is a son of Fire and wind, what that makes Him? An angry destroyer. But this simply comes from the fact that one observes a little fire-mishap and there must be a God behind it. Anyway above g is a y/j/i. which is why jal-na = to burn. [also gal-na; g as in egg is used, then put ni, ni-gal-na it becomes: to eat, to circumvent.]
[Fire even Fire = Pire, ire, inre, ignre]