IPA: /ˌpriːhɪˈstɔːrɪkli/
KK: /priːhɪˈstɔrɪkli/
In a way that relates to the time before written history.
The cave paintings were created prehistorically, long before any written records existed.
Prehistorically → It is formed from "pre-" (meaning before) and "history" (from Greek "historia", meaning inquiry or knowledge). The suffix "-ically" (meaning in a manner relating to) indicates the manner of something. Thus, "prehistorically" refers to the manner of events or conditions that existed before recorded history.
Think of 'pre-' meaning 'before' and 'history' as the record of past events. This helps you remember that 'prehistorically' refers to things that happened before history was recorded.