Please/Thank you in some European Languages

French;s'il vous plait
Greek;parakalo
Portugese;Por favor/obridago/a(male/female)
Spanish;por favor/gracias

Proto-Indo-European *sreu and its derivatives

This word meaning ` to flow' is the source of many cognates in Indo-European languages as well as placenames.

Danish/Swedish strom
Greek rheuma
Lithuanian srauna` a current'
Old Irish `sruaim' `river'
Sanskrit sravati

The Germanic languages acquired a `t' stween the `s' and the`r' as in other words eg. Stream
The Brythonic branch of Celtic seems to have `f' instead of `s' eg Welsh ffrwd,Cornish frot and Bretton froud.
Proto-Celtic *sraw-a-

Place-names possibly cognative to* sreu are
Charente/Cher/ Creuse/Sarthe/Seran in France (I am guessing on his one.)
Struma /Strymon river in Greece
Stryi river,west Ukraine
Cerglio/Serglio rivers, Italy(Guessing on this one as well!)