Aw, I shoulda guessed this was from my man Johnny Mercer, recorded by Bing Crosby for the 1936 movie Rhythm on the Range, and by Roy Rogers for the 1943 movie King of the Cowboys.

I'M AN OLD COWHAND (FROM THE RIO GRANDE)
(words & music by Johnny Mercer, 1936)
© 1936, John H. Mercer

Step aside you ornery Tenderfeet
Let a big bad buckaroo past
I'm the toughest hombre you'll ever meet
Tho' I may be the last.
Yessirree we're a vansishing race,
Nosirree can't last long.
Step aside you ornery Tenderfeet
While I sing my song.

I'm an old cowhand
From the Rio Grande
But my legs ain't bowed
And my cheeks ain't tanned,
I'm a cowboy who never saw a cow,
Never roped a steer 'cause I don't know how
And I sho' ain't fixin' to start in now.
Yippy I O Ki Ay,
Yippy I O Ki Ay.

I'm an old cowhand
From the Rio Grande
And I learned to ride,
'Fore I learned to stand
I'm a ridin' fool who is up to date
I know every trail in the Lone Star State
'Cause I ride the range in a Ford V-Eight
Yippy I O Ki Ay,
Yippy I O Ki Ay.

I'm an old cowhand
From the Rio Grande
And I come to town
Just to hear the band,
I know all the songs that the cowboys know
'Bout the old corral where the doagies go
'Cause I learned them all on the radio
Yippy I O Ki Ay,
Yippy I O Ki Ay.

I'm an old cowhand
From the Rio Grande
Where the West is wild,
'Round the Border land
Where the buffalo roam around the Zoo,
And the Indians make you a rug or two...
And the old Bar-X is a Bar B Q
Yippy I O Ki Ay,
Yippy I O Ki Ay.


Source: Johnny Mercer: The Life, Times, and Song Lyrics of Our Huckleberry Friend, by Bob Bach and Ginger Mercer (1982), page 56

JRO