What is the optimum or abbreviate word for not transferred?

There's no single perfect abbreviation for "not transferred," as it depends on the context. Here are some options:

Formal:

* Not Xferd: (Especially for technical contexts)

* N/T: (Suitable for concise notes or reports)

* Not Transferred: (Clear and unambiguous)

Informal:

* Not Xfer: (Shorter and more casual)

* Not Sent: (If the emphasis is on the lack of sending)

The best choice depends on the specific situation and your audience. Consider clarity, formality, and common usage in your field when making your decision.