Sister Mary Aloysius Duff.

 Tough and disciplined,

disciplined and tough,

 that's Sister Mary Aloysius Duff,

of penance and mortification

 can never get enough,

doesn't mind cold water,

 likes a towel to be rough.

Firm in her views,

 she takes no guff,

no time for free thought

 or any of that stuff.

She has a friend

 who is much the same,

that's Sister Joseph Alacoque Kane.

She likes Sister Joseph,

 likes her hardihood,

her indifference to pain,

 even likes her name.

No, not Joseph,

well, maybe Alacoque,

but certainly Kane.