The encrypted letters OQv correspond to the ASCII binary patterns:
O=1001111, Q=1010001, v=1110110.
Each of these resulting letters is produced by XOR of the key 0111000 with the original letters of the 3-letter word.
XOR is a bitwise operation in which aXORb for a,b∈{0,1} is 1 only if a≠b, otherwise the result is 0.
So to get the result for each letter we have:
0111000
XOR
1110111=“w”
1001111=“O”
0111000
XOR
1101001=“i”
1010001=“Q”
0111000
XOR
1001110=“N”
1110110=“v”
So the 3-letter word is “wiN”.