Nova Derivativa Verba Latina, Pars Quadringentesima Tertia

[diaphanus]

"Nova Derivativa Verba Latina, Pars Quadringentesima Tertia"
"New Latin Derivatives, Part Four Hundred Three"

Yeah:

quastrum -i m. "thing that shakes"
[quatere "to shake" + -trum agent noun suffix]
[quatere + -tro-] stems
[QUAT + -tro-] root and stem
[quattro-] new stem
[quastro-] t becomes s
[quastrum] nominative singular