BELL 206 HELI PLT REQUESTS A SPECIFIC VFR DEP RTE YET FOLLOWS A DIFFERENT RTE AFTER TKOF; CREATING A CONFLICT WITH A DEP ACR WHILE XING A RWY AT HOU.

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I REQUESTED A 'PASADENA DEP' WHICH; WHEN EXECUTED; WILL HAVE THE ACFT FLY A NORTHERLY HDG THEN; MIDFIELD; A NE COURSE OF 060 DEGS TO SELECTED CHKPOINTS OUTBOUND FROM THE ARPT. I WAS CLRED TO WHAT I BELIEVED WAS A PASADENA DEP; AND RESPONDED WITH A 'CLRED FOR TKOF.' ON CLBING OUT; AT MIDFIELD; I TURNED MY COURSE TO 060 DEGS AND THEN I NOTICED AN AIRLINER ROLLING DIAGONALLY ON MY R SIDE (THEY WERE ON RWY 12). I SAW THEM ROTATE THEREAFTER. I LOOKED AT MY ALTIMETER AND SAW I WAS ALMOST 400 FT MSL; SPECULATED THAT I MUST HAVE BEEN AT ABOUT 300 FT WHEN THEY MOVED INTO MY FIELD OF VIEW. NO ACTION WAS NEEDED ON MY PART; SO I CONTINUED ON. I WAS ALMOST OUT OF THE HOBBY AIRSPACE WHEN THE AIRLINER MADE A COMMENT TO THE CTLR THAT THE HELI WAS 'UNACCEPTABLY CLOSE' AND DEBATED WITH THE CTLR ABOUT THE CIRCUMSTANCE. I WAS THEN REQUESTED TO CALL THE TWR AT MY EARLIER CONVENIENCE. I CALLED THE TWR AND SPOKE TO TWR SUPVR WHO RELAYED TO ME THAT HE HAD LISTENED TO THE RECORDING SEVERAL TIMES OF MY REQUESTED CLRNC AND I HAD REQUESTED THE 'PEARLAND DEP' (THIS DEP WOULD PUT ME ON A SOUTHERLY DEPARTING COURSE AWAY FROM THE ARPT AND NEVER XING ANY RWYS). SUPVR INDICATED THAT I REQUESTED WHAT I WAS CLRED FOR -- 'A PEARLAND DEP.' I DO NOT QUESTION HIM OR THE FINE CREW AT THE TWR; HOWEVER; MY INITIAL REACTION WAS SHOCK THAT I MADE SUCH A MISTAKE IN MY INITIAL REQUEST EARLIER; BUT IT DID HAPPEN AS EVIDENCED BY THE RECORDING. CONTRIBUTING FACTORS MAY BE DUE TO THE DEPS BEGINNING WITH THE LETTER 'P'; AND IN MY HASTE; I MAY HAVE REQUESTED A RTE THAT WAS INCORRECT. IN SHORT; REQUESTED A 'PEARLAND' WHILE THINKING 'PASADENA' DEP.