insert any specific keyword before any random keyword

how to paste something before keyword.
example:-
sentence = i am an software engineer.

i want paste something before any one keyword means any one random keyword.
every time it will select random keyword from and document and paste specific word before that random keyword.

example:-
specific word = cool

i want paste specific word before any random keyword of the document.
than sentence possibly like this
i am an cool software engineer. or
i am an software cool engineer. or
i am cool an software engineer.

means i want insert any specific keyword before any random keyword.

tell me code please
thanks in advance