The Collaborative International Dictionary of English v.0.48:
Pou sto \Pou sto\ (p[=oo] st[=o]; pou st[=o]). [Gr. poy^ stw^ where I may stand; -- from the reputed saying of Archimedes, "Give me where I may stand and I will move the whole world with my steelyard."] A place to stand upon; a locus standi; hence, a foundation or basis for operations. [Webster 1913 Suppl.]