A good example of the use of an infix to create a new English word. The infix is used to emphasise the adverb.
This type of affix is unusual in English, especially for new word coinage - usually we only use suffixes or prefixes, eg. -ism, -fy, -ation, inter-, trans-, cyber- etc.
Infixes used as a way to inflect stong verbs were used in Old English (OE), and some survive today eg. sink, sank, sunk. Weak verbs are inflected by use of a suffix, ie. -ed eg. paint, painted. This form has become the common way of inflecting new verbs.