on·slaught 
(ŏnslôt′, ôn-)
(ŏnslôt′, ôn-)n.
1. A violent attack.
2. An overwhelming outpouring: an onslaught of third-class mail.
[Alteration (influenced by obsolete slaughte, slaughter) of Dutch aanslag, a striking at, from Middle Dutch aenslach : aen-, on; see an- in the Appendix of Indo-European roots + slach, a striking.]