Muffing is the slang term for a sex act that involves fingering one or both of the inguinal canals of someone with a penis.
The term originated in the zine ‘Fucking Trans Women’, first published in 2010 in Iowa by a trans woman named Mira Bellweather. The publication was a thorough guide dedicated to enjoying sex as a trans woman and to educating anyone with trans women sexual partners.
By Bellwether’s terms, she describes muffing as "being [finger-]fucked in one or both of my inguinal canals," which are the "twin 'pockets' that are situated in the groin above and behind the testicles and scrotum."
Anatomy of the Inguinal Canals
The inguinal canals are the pair of short passages located in the anterior wall of the abdomen. They serve as a path between the internal and external abdominal structures, each passing parallel to the inguinal ligament, through the groin and out towards the external genitalia.
The length changes from childhood to adulthood, reaching a typical length of ~4-6 centimeters. Typically, everyone has a variation of them but they tend to be more pronounced where testicles are present because they are the channel by which the testicles descend from within the abdomen to the scrotal sac.
Behind where the scrotum attaches to the body, the inguinal canals end at the external inguinal orifices. These present as small holes just beneath the skin on either side. This pair of small depressions beneath the skin is sensitive to the touch, which can be quite pleasurable for some people.
Bellwether’s publication focused primarily on bodies where the penis and scrotum were still present because that was where her experience lay. However, in the case of gender confirmation surgery that involves removing external genitalia, these external inguinal orifices may remain accessible and sensitive.
Fingering a Trans Woman
Each person may have a different degree of comfort with how they refer to their external inguinal orifices. Bellwether refers to them as her “cunts” as much as their anatomical names but what works for one person may cause gender dysphoria in another. When engaging with any partner, it is good practice to understand what language they prefer for their body parts.
The aforementioned depressions can be stroked and stimulated by hand through the skin. By adding pressure to the area, a finger can slide into the hole beneath the skin and into the canal there as far as it is comfortable.
Stretching the Inguinal Canal
When one first starts muffing, it may take a while to stretch and accommodate a finger. With patience and adequate warmup, a relaxing of the area will occur to allow for more or deeper penetration. Discomfort from trying something new can happen. However, if pain is experienced, slow down or try again after more warming up.
Anyone who practices tucking (i.e. the act of hiding one’s penis, scrotum, and testicles between the legs or buttocks, which also involves pressing the testicles back up in the inguinal canals) or who has experienced muffing will find it easier to find their inguinal canals or direct a partner to them.