Dear Sir,

Why we call as Caesar S/w as Caesar II ?
is there any reason ?

Because the first Caesar died a long time ago.

Wasn't caesar a title, not a man?

Hmmmm - I suppose so.

CAESAR: (Computer Aided Engineering Stress Analysis Routines).
My understanding is that the first version of CAESAR II was just CAESAR, and the second version was called CAESAR II; but in those days, version numbers were... a young concept.
By the release of the third iteration, it was clear that version numbers should not be a part of the product name. This was largely because the sales and marketing material couldn't keep up with the software development pace.
Henceforth, the product name remained CAESAR II, plus a version number.
By my calculations, using the old naming system, we are now using software that would otherwise be called CAESAR XXIV.
At least, that's the way I tell the story.

No, the name was never CAESAR. The "II" appeared as part of the name with the first release.