egnis/ognis

Agni. The Indic word for fire. I always wondered if from this very word
of Indoeuropeans is something preserved in Rom.
An it is.In Rom. the group "gn" > "mn" see Latin "cognatus" > Rom.
"cumnat".

In this order there should be a word like "amni" in Rom. and it should
mean "fire". Is there a such word? No. but there is "amnar"= a piece of
steel wich is used for knocking the flint for making fire. The
composition is usual root + suff. "-ar".

thus egnis/ognis > amn(V) + ar > amnar, thus the word "amnar" is the
reflex of the IE word

Accepted etymology of amnar cf. DEX:

amnar, reg. amânar; from Latin "manuale".

Observation: The Rom. form is like the Indik and Hittite , where the /e/
or /o/ from egnis/ognis became /a/ ( see Indik "agni/-h", hittite
"Agnis")

Question: how is usualy explained the lost of "s" in compositum? For
instance, if "amnar" should have been a very ancient composition, them
the "amnisar" should be the expected form amnis +ar > amnisar.
But there is no trace of "s", thus there is the question. Was "s" elided
in compositions or the explanation should be the "s" was lost very long
time ago before the suffix "-ar" was added?

Alex