contraction of throughout.
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for thruout
There is thruout this section a varying degree of verbal agreement.Sources of the Synoptic Gospels
Carl S. Patton
The wires tonight will carry the word all over this land, into Australia, New Zealand and thruout the world.The Everett massacre
Walker C. Smith
This militia existed, in 1784, thruout Massachusetts (and Maine) as nine divisions of approximately five thousand men each.
And thruout these opening days the 1st Regiment was subjected to the very hardest test, in that nothing whatever happened to them.
Thruout the Civil War, marksmanship was a neglected factor in the training of both northern and southern armies.