Concatenate Account Name in Contact Name

Create a Workflow Rule:

Setup > Create > Workflows & Approvals > Workflow Rules > New Rule

Select Object: Contact

Evaluation Criteria

                Evaluate the role when a record is: Created and every time its edited.

Rule Criteria: Formula evaluates to true

Formula: NOT(CONTAINS( FirstName , Account.Name ))

Save & Next

Add Workflow Action > New Field Update

Field to Update: First Name 

Use a formula to set new value

Account.Name & ": " &  FirstName

Save

Done

Activate

Contact Object > New Record (Save)

Account Name in Contact Name