You Do Need power plug adapter while traveling from Swaziland to Ireland (Eire).

Here is Why You Need An Adapter

The outlet and plug type used in Ireland (Eire) is G and in Swaziland is M. This is how they look like.

Swaziland

In Swaziland, outlets of type M are in use.

Type M

Ireland (Eire)

In Ireland (Eire), outlets of type G are in use.

Type G