The SS Deirdre was the name used by the Klingons in a false distress call in 2267.
The Deirdre claimed to be a small freighter, under attack by a Klingon ship. It supposedly had a maximum speed of warp 2. The Klingons used the message to lure the USS Enterprise away from Capella IV during Captain Kirk's attempt to negotiate for Federation mining rights there. Presumably, this was an attempt to bolster the position of their own agent Kras and/or undermine Kirk.
According to the distress call, the Earth vessel was under heavy attack from Klingon vessels; two ships in their convoy were already damaged. Once the freighter's last reported position was reached the Enterprise's sensors found no debris, no residual particles, nor residual traces. Scotty pulled the microtapes of the call and realized that the captain of the Deirdre had called the Enterprise by name – something unlikely to occur, since there is little chance a freighter captain would know the Enterprise had been assigned to that sector. Scotty remained long enough to be certain, and then set a course back for Capella IV. Almost immediately, a new distress call was received, this time from the USS Carolina, lending credence to the fact that the distress call was fraudulent. (TOS: "Friday's Child")
- Presumably, there was a real SS Deirdre, since it seems reasonable to assume that any ship named in a distress call would be compared to a registry of known Federation shipping. The Deirdre was most likely named after the beautiful heroine Deirdre of Irish folklore.