Ac is a vowel sound of A, I am just not sure which one (sources are sketchy)

Anglo-Saxon Rune Poem (from ragweedforge.com)

The oak fattens the flesh of pigs for the children of men.
Often it traverses the gannet’s bath,and the ocean proves whether the oak keeps faithin honourable fashion.

Ac translates to Oak (as in the tree). The rune poem illustrates two benefits of the oak tree, a source of food for domestic animals (acorns used to feed pigs) and also it’s benefit as a wood used in making seafaring vessels.
Esoterically, Ac partakes of the many symbolic qualities of the oak tree. It is a une of longevity, much as oak trees can live for a very long time. It is nurturing, as it supplies food (like acorns which can be fed to pigs, but also can be worked and made edible for humans as well). It is strong, as Oak wood has a very dense structure, and is often used in construction for it’s strength. It was also used for doors for this reason, as they were often the first defense against unwanted intrusion. Oak trees also show their strength in their ability to survive lightning strikes because of the wood density, which keeps them from being blown apart. I remember visiting an old oak tree in Indiana, which had been struck by lightning once, and had survived for many years after that. So, the strength of Oak is also about endurance and fortitude. A relationship can be seen between Ur and Ac as runes of strength, with Ur being active strength, like muscle and force, where as Ac is more passive and subtle strength, that has tenacity, and doesn’t yield or give up easily.