Active accessories (cables, goosenecks, rigid extension tubes that go between the capsule and amplifier of a condenser microphone) were invented and patented by Schoeps in 1973 as part of the Colette series. They were called "active" because the capsule end of the cable (etc.) contains active circuity--equivalent to the first FET stage of the microphone's amplifier.
The second manufacturer to offer a variety of remote capsule extensions was Neumann, for the KM 100 series (their first interchangeable capsule series after they introduced a cardioid-only microphone, the KMF 4, that had a permanently-attached extension cable--it could ONLY be used with that extension cable in place). In order to honor Schoeps' patent, they put the active circuitry into the capsule heads rather than the extension cables / goosenecks / tubes. Thus their capsules were "active capsules" rather than the cables (etc.) being "active cables" (etc.).
After the Schoeps patent expired, Neumann discontinued the KM 100 series and replaced it with the KM-A and KM-D series, which use passive capsules and active extensions. It's a better system for people who work with interchangeable capsules, since you don't have to pay for the FET circuitry again and again in each capsule that you buy.
In the past, Neumann and AKG had both offered capsule extensions with no active circuitry in them. But those were quite limited in length and were an RFI and distortion hazard, since the connections were unbalanced and at VERY high impedance.
--On this board, the term "active" has come to mean any extension cable for a condenser microphone capsule, whether it is truly active or not. Of course that's a misnomer in some cases.
--best regards