未然形＋んが grammar?


> などと、目をキラッキラと輝かせながら、皆を **呑み込まんが** 如く両手を大きく広げる。

I know the general meaning of the sentence but what is the grammar phenomenon
of 未然形＋んが? Is it a fixed structure?




This can be remembered as a literary set phrase, but it's technically a
[remnant of the grammar of classical Japanese
(文語)](https://japanese.stackexchange.com/a/42724/5010). In modern Japanese,
it's 皆を呑み込もうとするかのように両手を大きく広げる.

  * **呑み込ま** : the 未然形 of 呑み込む
  * **ん** : the 連体形 of the classical volitional/conjecturing auxiliary [む](https://www.hello-school.net/haroajapa009010.htm). The 連体形 worked as a nominalizer in classic Japanese. よう(とすること) in modern Japanese.
  * **が** : the archaic possessive particle. の in modern Japanese.
  * **如く** : the 連用形 of the classical adjective-like auxiliary [如し](https://www.hello-school.net/haroajapa009030.htm). ように in modern Japanese.

Related:

  * [Auxiliary verb ん](https://japanese.stackexchange.com/q/23924/5010)
  * [Is there a difference between んがため and ために?](https://japanese.stackexchange.com/q/5396/5010)
  * [Verb ending in -ん with positive meaning?](https://japanese.stackexchange.com/q/72064/5010)
  * [meaning of ~に於るが如く](https://japanese.stackexchange.com/q/83026/5010)
  * [Why is there a が in 深淵に臨むが如し?](https://japanese.stackexchange.com/q/70684/5010)

