Comparative evidence

1.teu̯p, 1.steu̯p

• Lat. stupeō ‘be physically powerless’, ‘be numb’, ‘be sluggish’, ‘be torpid’, ‘be stunned’, ‘be dazed’, ‘be amazed’, ‘be astonished’ (OLD 1831‒32)

cum hic etiam tum semisomnus, stupri plenus stuperet (Cic. Ver. 5.95)
animus lassus curв confectus stupet (Ter. An. 304)
quae cum intuerer stupens (Cic. Rep. 6.18)

• Lat. stupescō ‘become dazed’ (OLD 1832)

• Lat. stupiditās ‘stupidity’, ‘silliness’ (OLD 1832)

• Lat. stupidus (physically ) ‘dazed’, ‘numb’ (by an emotional shock), ‘stunned’, ‘foolish’, ‘dull-witted’ (OLD 1832)

• Lat. stupor ‘numbness’, ‘torpor’, ‘bewilderment’, ‘dullness’ (of apprehension), ‘stupidity’ (OLD 1832)

• Lat. stuprō ‘have a sexual intercourse’, ‘defile’ (by licentious conduct) (OLD 1832)

• Lat. stuprum ‘dishonour’, ‘shame’ (illicit), ‘sexual intercourse’ (OLD 1832).

Commentary: de Vaan (EDL: 593) assumes a semantic development ‘struck’, ‘stunned’ > ‘dishonoured’ for Lat. stuprum.

Lat. stuppa “coarse flax”, “tow” (OLD 1832) is a borrowing from Gr. στύππη “coarse fibre of flax”, “tow”, see DEL: 658f.

References

EDL = M. de Vaan, 2008. Etymological Dictionary of Latin and the other Italic Languages. Brill.
DEL = A. Ernout, A. Meillet, 1967. Dictionaaire étymologique de la langue latine. Histoire de mots. 4th ed. Klincksieck
OLD = Oxford Latin Dictionary. Oxford University Press, 1968.