Is there a common name for the first order IIR averaging filter?
This is often called a leaky integrator, a special case of a first-order IIR lowpass filter. They are discussed in more detail in several previous questions:


Is a leaky integrator the same thing as a low pass filter?
Is there a technical term for this simple method of smoothing out a signal?
Designing a practical integrator
&quot;Low-pass filter&quot; in non-EE, software API contexts