Change one letter.

[Mottie]

Dern

 

[Captain Nemesis]

derv

 

[Mottie]

Perv

 

[Captain Nemesis]

Perk

 

[Mottie]

Pert

 

[Captain Nemesis]

Cert

 

[Scarlet Pimpernel]

Ceri

 

[Mottie]

Cero

 

[Scarlet Pimpernel]

Cero

That's either not English or it's an acronym.

 

[Mottie]

That's either not English or it's an acronym.

 

[Nige F]

aero

 

[Mottie]

Hero

 

[Captain Nemesis]

zero

 

[Mottie]

Nero

 

[Captain Nemesis]

Nerd